1. Field of the Invention
The present invention relates to a method for producing a polyester resin particle dispersion material, a method for producing polyester resin particles and a method for producing an electrophotographic spherical toner. More particularly, the present invention relates to a method for producing a polyester resin particle dispersion material, a method for producing polyester resin particles and a method for producing an electrophotographic spherical toner, in which the average particle size can be easily controlled within a broad range and is less likely to form irregular particles such as string-shaped particles, and which is also suited for use in adhesives such as hot-melt adhesive.
2. Description of Related Art
As a method for producing polyester resin particles or an aqueous dispersion material thereof without using an emulsifier, for example, a method of dispersing a colored resin melt comprising a polyester resin having a carboxyl group and a colorant in an aqueous medium containing a basic compound to form an aqueous dispersion material in a melted state, and cooling and drying the aqueous dispersion material is disclosed in Japanese Unexamined Patent Application, First Publication No. Hei 9-311502, while a method of dispersing a melt of a polyester resin having a carboxyl group, which is obtained by polymerizing a polyhydric alcohol and a polyhydric carboxylic acid with a compound having an alkyl group and an epoxy group, in an aqueous medium containing a neutralizer in a melted state to form an aqueous dispersion material is disclosed in Japanese Unexamined Patent Application, First Publication No. 2000-191892.
Although resin particles containing a relatively large amount of spherical particles are obtained when using a non-branched linear polyester resin according to these methods, the resin particles must be classified when used as a toner because of broad particle size distribution. When using a branched polyester resin to obtain particles for am adhesive having excellent adhesive strength and water resistance and a toner having excellent fixation properties at low temperatures and anti-offset properties, toner particles, among which there are a large number of irregular particles such as string-shaped particles, are likely to be produced. Therefore, the solid content of the dispersion material must be reduced to 20% by weight, thereby causing a problem that the production efficiency is lowered. Moreover, according to these methods, it is not easy to control the average particle size of the polyester resin and to arbitrarily set the average particle size of the polyester resin particles within a broad range from 0.05 to 500 xcexcm.
An object of the present invention is to provide a method for producing a polyester resin particle dispersion material composed of spherical polyester resin particles and a method for producing polyester resin particles, which can easily control an average particle size within a broad range and is less likely to form irregular particles such as string-shaped particles, and a method for producing an electrophotographic spherical toner, which can easily control an average particle size within a broad range and is less likely to form irregular particles such as string-shaped particles, and which is also superior in fluidity and durability and is capable of producing toner particles having a narrow particle size distribution.
As a result of diligent research, the present inventors have found that, when using, as a polyester resin having a carboxyl group, a polyester resin (A) having a terminal structure in which an alkyl group having 4 to 20 carbon atoms or an alkenyl group having 4 to 20 carbon atoms is bonded to a carbon atom to which a carboxyl group is attached, or a carbon atom adjacent to this carbon atom, in the case of producing a polyester resin particle dispersion material or an electrophotographic spherical toner by dispersing a melt of a polyester resin having a carboxyl group described in Japanese Unexamined Patent Application, First Publication No Hei 9-311502 or Japanese Unexamined Patent Application, First Publication No. 2000-191892 in an aqueous medium containing a basic compound in a melted state, it is made possible to obtain a polyester resin particle dispersion material composed of spherical polyester resin particles having a narrow particle size distribution, which can easily control an average particle size within a broad range and is less likely to form irregular particles such as string-shaped particles, and which is also suited for use in adhesives such as hot-melt adhesives even if the polyester resin (A) is a linear polyester resin or a branched polyester resin and the dispersion material has a high solid content. Also, we have found that when using the polyester resin (A) in combination with a colorant (B) and using a branched polyester resin as the polyester resin (A), it is made possible to obtain an electrophotographic spherical toner, which can easily control an average particle size within a broad range and is less likely to form irregular particles such as string-shaped particles, and which is also superior in fluidity and durability and is capable of producing toner particles having a narrow particle size distribution. Thus, the present invention has been completed.
The present invention provides a method for producing a polyester resin particle dispersion material, which comprises dispersing a resin melt containing, as an essential component, a polyester resin (A) having a terminal structure in which an alkyl group having 4 to 20 carbon atoms or an alkenyl group having 4 to 20 carbon atoms is bonded to a carbon atom to which a carboxyl group is attached, or a carbon atom adjacent to this carbon atom, a portion or all of the carboxyl groups in the polyester resin (A) being neutralized with a basic compound, in a heated aqueous medium in a melted state, and cooling the dispersed resin melt.
The present invention also provides a method for producing polyester resin particles, which comprises producing a polyester resin particle dispersion material by the method, and drying the polyester resin particle dispersion material.
The present invention also provides a method for producing an electrophotographic spherical toner, which comprises dispersing a resin melt containing, as an essential component, a polyester resin (A) having a terminal structure in which an alkyl group having 4 to 20 carbon atoms or an alkenyl group having 4 to 20 carbon atoms is bonded to a carbon atom to which a carboxyl group is attached, or a carbon atom adjacent to this carbon atom and a colorant (B), a portion or all of carboxyl groups in the polyester resin (A) being neutralized with a basic compound, in a heated aqueous medium in a melted state, and cooling and drying the dispersed resin melt.
According to the method for producing a polyester resin particle dispersion material and the method for producing polyester resin particles of the present invention, it is made possible to easily control the average particle size within a broad range and to easily produce a dispersion material composed of spherical polyester resin particles with fewer irregular particles such as string-shaped particles. Also, according to the method for producing an electrophotographic spherical toner of the present invention, it is made possible to easily control the average particle size within a broad range and to efficiently produce toner particles with fewer irregular particles such as string-shaped particles, which are superior in fluidity and durability and have a narrow particle size distribution.